Late Quaternary stratigraphy, glacial limits and paleoenvironments

Marresale area, western Yamal Peninsula, Russia

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Ice-sheet reconstructions for the last glacial maximum in northern Eurasia range from nearly complete coverage by a contiguous marine-based ice sheet to largely unglaciated. Stratigraphic records from coastal cliff sections near the Marresale Station on the Yamal Peninsula yield new insight on the eastern extent of the Eurasian ice sheet in the Kara Sea. Field studies identify nine informal stratigraphic units from oldest to youngest: the Marresale formation, Labsuyakha sand, Kara diamicton, Varjakha peat and silt, Oleny sand, Baidarata sand, Betula horizon, Nenets peat and Chum sand that show a single glaciation and a varied terrestrial environment during the late Pleistocene. The Kara diamicton reflects regional glaciation and is associated with glaciotectonic deformation from the southwest of the underlying Labsuyakha sand and Marresale formation. Finite radiocarbon and luminescence ages of c. 35 to 45 ka from Varjakha peat and silt that immediately overlies Kara diamicton, place the glaciation >40 ka ago. Eolian and fluvial deposition ensued with concomitant cryogenesis between c. 35 and 12 cal ka associated with the Oleny and the Baidarata sands. There is no geomorphic or stratigraphic evidence of coverage or proximity of Yamal Peninsula to a Late Weichselian ice sheet. The Nenets peat accumulated over the Baidarata sand during much of the past 10 ka, with local additions of the eolian Chum sand starting c. 1 ka ago. A prominent Betula horizon at the base of the Nenets peat contains rooted birch trees c. 10 to 9 cal ka old that indicates a >200 km shift northward of treeline from present limits, which reflects a 2 to 4 ?C summer warming across northern Eurasia.